U.S. law enforcement officials say they are being thwarted in solving dozens of criminal cases because they cannot access incriminating information that suspects have stored in encrypted files on their cellphones equipped with the latest technology.

New York City Police chief of intelligence Thomas Galati told the House of Representatives investigations panel Tuesday his officers "have the legal right to open [information in suspects' phones], but not the technical expertise." He said police once relied on wiretaps to listen to suspects plotting crimes, but "now we are likely in the dark."

The debate about whether protecting the public's right to privacy is more important than the need by authorities to halt terrorist activity and everyday crimes has taken on a new urgency in the United States, as Apple and other technology companies sell devices with tough-to-crack encrypted features.

During the congressional hearing, one Federal Bureau of Investigation official, Amy Hess, said encryption "renders suspects virtually anonymous on the Internet." She said investigators at the FBI, the country's top law enforcement agency, are seeing criminals "urging others to move to encrypted devices."

The issue has figured prominently in the investigation of Syed Rizwan Farook, an American-born Muslim, who with his Pakistani--born wife, Tashfeen Malik, shot 14 people to death at a local government center in San Bernardino, California, last December. Authorities say it was an attack inspired by overseas terrorists.

The FBI sued to force Apple to develop software to crack into Farook's iPhone, but the technology giant refused, saying it would endanger the security of the phones for millions of its customers. The FBI abruptly dropped the lawsuit and paid hackers to break into Farook's phone, although it is not known what information was stored on it

The chairman of the House panel, Republican Tim Murphy, said encryption has given criminals "a cloak of invisibility. It's pretty frightening."

A police intelligence official in the midwestern state of Indiana, Charles Cohen, said Apple has developed cellphones "without a key." He added that some suspects remain free because possibly incriminating evidence on their cellphones is "completely out of reach" for police.

The lawmakers listening to the complaints about the information being hidden on encrypted devices said they want to devise some middle ground policy on access to the information, protecting privacy rights while also allowing law enforcement officials access to incriminating evidence they need to arrest and convict criminals and terrorists.